**4. Prediction of silent ischemic lesions after carotid artery stenting using IBS and MRI**

Carotid artery stenting (CAS) has recently emerged as a potential alternative to carotid endarterectomy (CEA) [13] because it is a less invasive procedure and results in a shorter duration of hospitalization. Although many advantages of CAS have been reported, one of its disadvantages is the considerably high incidence of distal emboli during CAS, even though they are subclinical. Asymptomatic or silent ischemic lesions were detected by diffusionweighted magnetic resonance imaging (DWI) more often in CAS than in CEA patients [14]. We and other investigators reported that analysis of carotid plaques using IBS ultrasound or black-blood magnetic resonance imaging (BB-MRI) can identify the histological components of carotid plaques [9, 12, 15].

We evaluated carotid lesion with stenosis with a symptomatic carotid stenosis of > 70% or an asymptomatic carotid stenosis of > 60% assessed with angiography, as recommended by the North American Symptomatic Carotid Endarterectomy Trial collaborators [16]. In IBS analysis, relative unstable component area (%UCA: area of intra-plaque hemorrhage and lipid pool / area of plaque) were automatically measured in each plaque by computer software (T3D, Fortner Research LLC, Sterling, Virginia). IN MRI analysis, we calculated the ratio of the signal intensity of carotid plaques to that of sternocleidomastoid muscle and defined this as the signal intensity ratio (SIR). We assessed newly appearing ipsilateral silent ischemic lesions (NISIL) detected by diffusion-weighted magnetic resonance imaging (DWI) before and after CAS. At the same time, we performed quantitative analysis of plaque characteristics using IBS ultra‐ sound and BB-MRI before CAS in all patients.

After CAS, DWI showed 94 silent ischemic lesions in 19 patients (38%) (diffusion positive group; P group). There were no differences in baseline patient characteristics between the P group and diffusion negative group (N group). In the P group, %UCA analyzed by IBS was significantly higher than in the N group (60.2 ± 23.4% and 35.3 ± 19.2%, respectively, p<0.001). Also, the SIR of most stenotic lesions of carotid plaques analyzed by T1WI of BB-MRI was significantly higher in the P group than in the N group (1.40 ± 0.19 and 1.18 ± 0.25, respectively, p<0.01) (Figure 3). In multivariate logistic regression analysis, the independent predictors of NISIL were SIR (p = 0.030), the CRP level (p = 0.041) and the %UCA measured by IBS (p = 0.049). In the analysis of receiver operating characteristic curves, 50% of the %UCA measured by IBS analysis and an SIR of 1.25 measured by BB-MRI analysis were determined as the most reliable cutoff values for predicting NISIL. Using these cutoff values, the respective positive and negative predictive values were 76% and 82% in the IBS analysis and 62% and 88% in the BB-MRI analysis.

**Figure 2.** Representative images of three dimensional IBS color-coded maps. Left: Three-dimensional cut out images of color-coded maps of carotid arteries. Middle: Three-dimensional images of lipid pool. Right: High resolutional mag‐

**4. Prediction of silent ischemic lesions after carotid artery stenting using**

Carotid artery stenting (CAS) has recently emerged as a potential alternative to carotid endarterectomy (CEA) [13] because it is a less invasive procedure and results in a shorter duration of hospitalization. Although many advantages of CAS have been reported, one of its disadvantages is the considerably high incidence of distal emboli during CAS, even though they are subclinical. Asymptomatic or silent ischemic lesions were detected by diffusionweighted magnetic resonance imaging (DWI) more often in CAS than in CEA patients [14]. We and other investigators reported that analysis of carotid plaques using IBS ultrasound or black-blood magnetic resonance imaging (BB-MRI) can identify the histological components

We evaluated carotid lesion with stenosis with a symptomatic carotid stenosis of > 70% or an asymptomatic carotid stenosis of > 60% assessed with angiography, as recommended by the North American Symptomatic Carotid Endarterectomy Trial collaborators [16]. In IBS analysis, relative unstable component area (%UCA: area of intra-plaque hemorrhage and lipid pool / area of plaque) were automatically measured in each plaque by computer software (T3D, Fortner Research LLC, Sterling, Virginia). IN MRI analysis, we calculated the ratio of the signal intensity of carotid plaques to that of sternocleidomastoid muscle and defined this as the signal

netic resonance images of carotid plaques.

22 Carotid Artery Disease - From Bench to Bedside and Beyond

of carotid plaques [9, 12, 15].

**IBS and MRI**

**Figure 3.** Representative images of CAS for an internal carotid plaque that consisted of less unstable component. (A) Pre-steting angiogram of the left internal carotid artery stenosis. (B) White arrow: Axial image of the most stenotic lesion of the plaque on T1WI of BB-MRI. \*: sternocleidomastoid muscle. The SIR was 1.37 (C) Cross-sectional color-cod‐ ed map of the most stenotic lesion of the plaque on IBS. Relative unstable component area was 62%. (D) Post-stenting angiogram of the left internal carotid artery stenosis. After carotid artery stenting, the lumen of the right internal caro‐ tid artery was successfully dilated. (E) Diffusion-weighted magnetic resonance imaging. White arrows: multiple silent ischemic lesions are detected in the left cerebral hemisphere after the post-stenting procedure.
